Semiconductor device features continue to decrease in size as the demand for faster and smaller electronic devices increases. As the spacing between conductive features (e.g., metal lines) decreases, the likelihood of capacitive coupling between the conductive features increases. To address this problem, low dielectric constant insulator layers (e.g., k<4.0) or “low k” dielectric layers are being increasingly used by the semiconductor industry to reduce capacitive coupling between adjacent metal lines. Porous dielectric layers are low k dielectric layers since they use air (which has a dielectric constant of approximately 1.0) as a partial dielectric medium.
Sol gel processes can be used to form porous dielectric layers. In a typical sol gel process, a sol gel layer is spin coated on a substrate using a sol gel solution. The sol gel solution may include a mixture of chemical compounds, water, and surfactant. After depositing the sol gel layer on the substrate, the substrate and the sol gel layer are heated to cure it. During the curing process, water and other components of the sol gel solution (e.g., surfactant) are removed from the sol gel layer. The chemical compounds form particles that bind together forming a porous dielectric layer.
After the porous dielectric layer is formed, the porous dielectric layer may be placed in a stripping chamber. In the stripping chamber, any remaining surfactant can be removed from the porous dielectric layer. Then, a thin capping layer may be formed on the porous dielectric layer.
The curing process that is used in the sol-gel process can be a “batch” process. In a batch curing process, many substrates with sol gel layers on them are heated simultaneously in the same manner and in the same curing chamber. After all of the sol gel layers on all of the substrates are cured, all of the substrates are removed from the curing chamber.
Although batch curing processes are useful, improvements could be made. For example, a batch curing process can take longer than prior or subsequent processes such spin coating and capping layer processes. As a result, the curing process can be considered the gate in the overall process flow and processing apparatuses that are used before and after the curing process may sit idle while waiting for the curing apparatus to cure the current batch of substrates.
It would be desirable to provide for a heating apparatus that can continuously process substrates. This would maximize the use of each apparatus in the overall process and would reduce the cycle times for the substrates being processed.
Embodiments of the invention address this and other problems.